to explain something by talking about it in detailexpound something (to somebody)He expounded his views on the subject to me at great length.the theory of language expounded by ChomskyShe expounded her theory further in the course of her talk.These ideas were originally expounded by Plato.expound on somethingWe listened as she expounded on the government's new policies.Word OriginMiddle Englishexpoune (in the sense ‘explain (what is difficult)’): from Old Frenchespon-, present tense stem of espondre, from Latinexponere

‘expose, publish, explain’

, from ex-

‘out’

+ ponere

‘put’

. The origin of the final -d (recorded from the Middle English period) is uncertain (compare with compound, propound).